Defective pixel correction method and system

ABSTRACT

A defective pixel detection and correction mechanism for use in an image sensor integrated circuit determines whether a current pixel is a defective pixel in a consistent manner from frame to frame. The defective pixel detection and correction mechanism also replaces defective pixels with stable replacement values. The defective pixel detection and correction mechanism has a defective pixel detection mechanism that employs a look-up table with defective pixel locations for providing a non-varying determination of whether a pixel is defective or non-defective. The defective pixel detection and correction mechanism also has a defective pixel correction mechanism that employs a consistent replacement choice facility to provide a previous pixel value in the same frame, on the same row, and a predetermined number of pixels from the current pixel location as a replacement value and a replacement unit (e.g., multiplexer) for replacing the defective pixel value with the replacement value.

FIELD OF THE INVENTION

The present invention relates generally to image sensors, and moreparticularly, to a defective pixel correction method and system forimage sensors.

BACKGROUND OF THE INVENTION

Recent years have seen a proliferation of digital cameras, such asdigital still cameras and digital video cameras. There are many consumerapplications that require digital image capture. These applications caninclude, for example, still motion imaging, full motion imaging,security and surveillance applications, and video-conferenceapplications. An important component in digital still cameras anddigital video cameras is the image sensor integrated circuit. Imagesensor integrated circuits employ an array of pixels (e.g., a 640×480pixel array) for detecting photons of light and for converting thephotons into an electrical signal (e.g. voltage).

Most image sensor integrated circuits are manufactured by utilizing acomplimentary metal oxide semiconductor (CMOS) process. Unfortunately,as with any manufacturing process, image sensor parts have defectivepixels. Customers of these parts do not wish to have any obviousdefective pixels.

One approach to address defective pixels is to establish strict blemishspecifications. For example, vendors of image sensor integrated circuitsestablish blemish specifications that prevent the shipment of sensorswith more than a predetermined number of defects, with defects incertain locations, or with certain types of defects. Unfortunately, theblemish specifications result in lower yields and lower volumes for themanufacturer of the image sensors and higher costs for the customers.

A second approach to address the defective pixel problem is to use sometype of defective pixel correction scheme. There are some CCD imagesensors that have built-in hardware for use in correcting defectivepixels. Unfortunately, these implementations require complex hardwarecomponents that occupy a large physical space, thereby making the schemeexpensive to implement. Accordingly, these expensive and cumbersomesolutions are relegated to only a few applications (e.g., high-end andlow-volume applications).

Another hardware approach is described in a semiconductor technical dataentitled, “Digital Image Sensor—SCM20014,” available from Motorola, Inc.Motorola's digital image sensor decides that pixels are defectiveindependently from frame to frame and then corrects the defective pixelsby replacing them with a varying value derived from neighboring pixelsfor that particular frame. Unfortunately, as described in greater detailhereinafter, this approach utilizes a detection and correction techniquethat can vary from frame to frame, thereby leading to undesirable imageartifacts.

Moreover, some have proposed the use of software-based defective pixelcorrection techniques. Unfortunately, these prior art approaches requirea processor with sufficient processing power to execute the softwarealgorithms that perform the defective pixel correction. As can beappreciated, these software techniques are not available to productsthat do not have a processor. Furthermore, even for those products thathave a processor, the software techniques consume large amounts ofprocessor bandwidth, which may not be acceptable to other componentsthat also require the processor bandwidth. As can be appreciated, therequirement of these software-based techniques for a processor increasesthe cost of such a product so that such an approach is also relegated tohigh-end image capture devices.

Some have proposed the use of a personal computer (PC) that can becoupled to a digital capture device (e.g., a digital camera) to executethe correction techniques. In such an approach, the digital capturedevice first sends the image with the defective pixels to the PC, andthen the PC executes the defective pixel correction schemes to correctthe image. An advantage of this approach is that the hardware requiredin the digital capture device can be simplified since the processingpower of the PC is harnessed for executing the defective pixelcorrection software. Unfortunately, most PC connectable capture devicesperform data compression on the image in order to transfer the data tothe PC through a link (e.g., a USB cable). When compression is appliedto the image, there is a high likelihood that the defects spread out andthe appearance of the image becomes worse, making correction at the PCmore difficult. Consequently, it is desirable to perform defective pixelcorrection in the sensor IC.

Furthermore, these prior art approaches provide 1) inconsistentdefective pixel detection, and 2) inconsistent defective pixelcorrection, thereby causing undesirable artifacts in the resultingimage.

One disadvantage of these prior art approaches is that the defectivepixel detection may determine that a particular pixel is defective inone frame and not defective in another frame (hereinafter referred to asinconsistent defective pixel detection). As can be appreciated,inconsistent defective pixel detection provides inconsistent resultsfrom frame to frame, thereby leading to a loss of resolution at a pixellocation. For example, in a first frame a particular pixel may bedetermined to be a defective pixel that is replaced with another value.In another frame, the same pixel may be determined to be a non-defectivepixel that retains its pixel value. When this approach is applied in adigital video capture device, the inconsistent detection can causeartifacts in the resulting video, such as a blinking spot. Similarly,when the approach is applied in a digital still camera, the inconsistentdetection can cause artifacts (e.g., a bright spot or spots) in theresulting image. Consequently, it would be desirable for there to be adefection pixel correction mechanism that consistently detects defectivepixels from frame to frame.

Another disadvantage of this approach is that the defective pixelcorrection may replace the defective pixel value with differentreplacement choices from frame to frame (hereinafter referred to asinconsistent defective pixel correction). For example, in a first framea pixel that is determined to be defective is replaced with a firstvalue. In a second frame the same pixel that is defective may bereplaced with a second value. In a digital still image, inconsistentreplacement values for adjacent pixels may not be critical. However, fordigital video, an inconsistent replacement value from frame to frame isvery noticeable to the human eye. For example, a replacement value thatvaries for a defective pixel from frame to frame may appear to the humaneye as a blinking spot in the video.

Based on the foregoing, there remains a need for a defective pixelcorrection method and system for image sensors that overcomes thedisadvantages set forth previously.

SUMMARY OF THE INVENTION

According to one embodiment of the present invention, a defective pixeldetection and correction mechanism for use in an image sensor integratedcircuit is provided. The defective pixel detection and correctionmechanism determines whether a current pixel is a defective pixel in aconsistent manner from frame to frame. The defective pixel detection andcorrection mechanism also replaces defective pixels with consistentreplacement choices.

In one embodiment, the defective pixel detection and correctionmechanism has a defective pixel detection mechanism that employs alook-up table with defective pixel locations for providing a non-varyingdetermination of whether a pixel is defective or non-defective. Thedefective pixel detection and correction mechanism also has a defectivepixel correction mechanism that employs a consistent replacement choicefacility to provide a previous pixel value in the same frame, on thesame row, and a predetermined number of pixels from the current pixellocation as a replacement pixel value. A replacement unit (e.g.,multiplexer) is provided for replacing the defective pixel value withthe replacement value.

According to another embodiment of the present invention, a defectivepixel detection and correction method for use in correcting defectivepixels in an image sensor integrated circuit is provided. First, acurrent pixel location is received. Second, a defective pixel locationis received. Next, a determination is made whether the current pixellocation is a defective pixel location. When the current pixel locationis not a defective pixel location, providing a received pixel value(e.g., a value received from the analog to digital converter (ADC)) asoutput pixel value. When the current pixel location is a defective pixellocation, providing a previous pixel value (e.g., a previous pixel valuethat is in the same frame, same row, and a predetermined number ofpixels from the current pixel locations) as the output pixel value.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings and in whichlike reference numerals refer to similar elements.

FIG. 1 is a block diagram illustrating an exemplary image sensor inwhich the defective pixel detection and correction mechanism (DPDCM) ofthe present invention can be implemented.

FIG. 2 illustrates in greater detail the defective pixel detection andcorrection mechanism (DPDCM) of FIG. 1 in accordance with one embodimentof the present invention.

FIG. 3 illustrates in greater detail the defective pixel detectionmechanism (DPDM) and the defective pixel correction mechanism (DPCM) ofFIG. 2 in accordance with one embodiment of the present invention.

FIG. 4 is a flowchart illustrating the processing steps performed by thedefective pixel detection and correction mechanism (DPDCM) of FIG. 2.

FIG. 5 illustrates an exemplary defective pixel location table.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A defective pixel correction method and system for image sensors aredescribed. In the following description, for the purposes ofexplanation, numerous specific details are set forth in order to providea thorough understanding of the present invention. It will be apparent,however, to one skilled in the art that the present invention may bepracticed without these specific details. In other instances, well-knownstructures and devices are shown in block diagram form in order to avoidunnecessarily obscuring the present invention.

Exemplary Image Sensor 100

FIG. 1 is a block diagram illustrating an exemplary image sensor 100 inwhich the defective pixel detection and correction mechanism (DPDCM) 110of the present invention can be implemented. The image sensor 100includes a sensor array 120 having a plurality of pixels 122 that arearranged in rows and columns. The image sensor 100 also includes rowselect logic 130 (hereinafter referred to as row selector) for selectinga row of the array 120 and a column select logic 140 (hereinafterreferred to as column selector) for selecting a particular column in thearray 120. Together, the row selector 130 and the column selector 140specify a particular pixel in the array 120 for access (e.g. an accessto read the value at the pixel).

The image sensor 100 also includes a timing controller 150, whoseconstruction and operation is well known by those of ordinary skill inthe art, for providing various control signals to components in thesensor 100. For example, the timing controller 150 provides signals tocontrol the row selector 130 and the column selector 140.

The image sensor 100 also includes an amplifier 160 that is coupled tothe output of the sensor array 120 for amplifying the output of thesensor array 120 and an analog to digital converter (ADC) 170 that iscoupled to the amplifier 160 for converting the analog pixel values intocorresponding digital pixel values. The timing controller 150 alsoprovides signals to control the ADC 170.

The image sensor 100 can include the defective pixel detection andcorrection mechanism (DPDCM) 110 of the present invention. The defectivepixel detection and correction mechanism (DPDCM) 110 detects andcorrects of defective pixels in a stable and consistent manner, therebyreducing artifacts that stem from inconsistent detection and correctionof defective pixels. The DPDCM 110 employs a look-up table withdefective pixel locations for enabling consistent defective pixeldetection and a consistent replacement choice facility for enablingstable defective pixel correction. The defective pixel location tableand consistent replacement choice facility are described in greaterdetail hereinafter with reference to FIG. 2.

The DPDCM 110 includes a first input that is coupled to the ADC 170 forreceiving the digital value of a current pixel. The DPDCM 110 alsoincludes a plurality of inputs that are coupled to the timing controller150 for receiving a plurality of signals therefrom. In this embodiment,the plurality of signals includes a start frame signal for indicatingthe start of a new frame, a start row signal for indicating the start ofa new row, a current row signal for indicating a current row, and acurrent column signal for indicating a current column.

The DPDCM 110 also includes an input that is coupled to a sensorprogramming path 154. The sensor programming path 154 is provided toallow an external source (e.g., a designer or a component external tothe DPDCM 110) to program and control the DPDCM 110. For example, thesensor programming path 154 can be utilized to program the look-up tablewith defective pixel locations that are determined, for example, by amanufacturing test. The sensor programming path 154 can include anenable signal that can be utilized to enable or disable the DPDCM 110 byselectively asserting or de-asserting the enable signal.

Based on these inputs, the DPDCM 110 determines whether a current pixellocation is a defective pixel location. When the current pixel locationis not a defective pixel location, the DPDCM 110 provides the pixelvalue received from the ADC 170 as an output pixel value. When thecurrent pixel location is a defective pixel location, the DPDCM 110provides a previous pixel value as the output pixel value. For example,the previous pixel value can be in the same frame, on the same row, anda predetermined number of pixels away from the current pixel.Preferably, the previous pixel is of the same color and two pixellocations to the left of the current pixel. The DPDCM 110 is describedin greater detail hereinafter with reference to FIG. 2 and FIG. 3.

It is to be appreciated that the image sensor 100 can be implemented asa stand-alone integrated circuit for use with other integrated circuits(e.g., for use in chip set) or incorporated as a functional block in anapplication specific integrated circuit (ASIC). One aspect of thepresent invention is an efficient, space-saving, hardware implementationof a defective pixel detection and correction mechanism that obviatesthe need for processing power (e.g., a processor) required by prior artsoftware techniques. Another advantage of the present invention is thatthe correction mechanism can be implemented in the sensor chip 100. Thepixel correction mechanism of the present invention provides consistentdefective pixel detection and consistent defective pixel correction withstable replacement values for the defective pixels.

Defective Pixel Detection and Correction Mechanism (DPDCM)

FIG. 2 illustrates in greater detail the defective pixel detection andcorrection mechanism (DPDCM) 110 of FIG. 1 in accordance with oneembodiment of the present invention. It is noted that the DPDCM 110 canbe implemented in a post ADC processing block 204 that performs digitalsignal processing on post ADC digital image data.

The DPDCM 110 includes a defective pixel detection mechanism (DPDM) 210and a defective pixel correction mechanism (DPCM) 220 for eliminatingartifacts that stem from inconsistent detection and artifacts that stemfrom inconsistent correction of defective pixel. respectively.

The defective pixel detection mechanism (DPDM) 210 provides adetermination of whether a current pixel location is a defective pixellocation in a manner that does not vary from frame to frame. In thepreferred embodiment, the defective pixel detection mechanism 210employs a look-up table with a plurality of defective pixel locationsfor enabling the consistent detection of defective pixels.

The defective pixel correction mechanism (DPCM) 220 replaces a currentdefective pixel with a previous pixel value that is a consistentreplacement choice. Preferably, the previous pixel value is from thesame frame, on the same row, and a predetermined number of pixels fromthe current defective pixel location (e.g., two pixels to the left ofthe current pixel location). The defective pixel correction mechanismemploys a consistent replacement choice facility 254 to provide aprevious pixel value in the same frame, on the same row, and apredetermined number of pixels from the current pixel location as areplacement pixel value. A replacement unit 250 (e.g., multiplexer) isprovided for replacing the defective pixel value with the replacementvalue.

FIG. 3 illustrates in greater detail the defective pixel detectionmechanism (DPDM) and the defective pixel correction mechanism (DPCM) ofFIG. 2 in accordance with one embodiment of the present invention.

Defective Pixel Detection Mechanism 210

The defective pixel detection mechanism 210 includes a look-up table 230for storing defective pixel locations, a register 234 for use inaccessing (e.g., reading or writing) the defective pixel locations, anindex 238 for pointing to a particular defective pixel location in thetable 230, and an index manager 242 (e.g., an incrementer) for managingthe index 238.

In the preferred embodiment, the defective pixel locations in the lookuptable 230 are stored in a sorted order. In this manner, no search of thetable is required, thereby saving hardware components and space.Furthermore, the last table entry is preferably coded as a non-existinglocation (e.g., a location that is off the end of the pixel array). Inthis manner, the last table entry is guaranteed never to match a currentrow and current column, and so the index is never incremented beyond thelast entry. Consequently, no limit check need be performed on the lookuptable index, thereby saving hardware components and space.

These enhancements to the lookup table 230 enable the defective pixelcorrection mechanism to be implemented in an even more efficient andcost-effective manner. By simplifying the hardware needed to implementthe correction mechanism, the amount of physical space occupied isfurther reduced as compared with prior art approaches.

When the defective pixel locations are stored in a sorted order, theindex manager 242 can be implemented with an incrementer that simplyupdates the index 238 (e.g., incrementing the index by one) wheneverthere is a match so that the index 238 points to the next defectivepixel location in the table 230.

Exemplary Defective Pixel Location Table 230

FIG. 5 illustrates an exemplary configuration for the defective pixellocation table 230. The table 230 can include a plurality of defectivepixel locations (e.g., a first location, a second location, a thirdlocation and an Nth location). Each location can have a row value (e.g.,ROW_(—)1, ROW_(—)2, . . . , ROW_N) and column value (e.g., COL_(—)1,COL_(—)2, . . . , COL_N) for specifying a pixel location in the array ofpixels that is defective. The index manager 238 is employed to manage atable index 239 that points to one of the defective pixel locations. Theindex manager 238 has an input for receiving a start frame signal andresponsive thereto for resetting the table index so that the indexpoints to the first defective pixel location.

The index manager 238 can manage the index 239, for example, byincrementing the table index every time there is a match between thecurrent pixel location and the current defective pixel location. In thisregard, the index manager 238 can employ an incrementer that isresponsive to the match signal for selectively updating the index 239 byone.

The defective pixel detection mechanism 210 also includes a match unit240 that has a first input for receiving the current row and currentcolumn, a second input for receiving a next defective pixel location,and a third input for receiving an enable signal. The match unit 240 isprovided to determine whether a current row and current column matchwith a row and column, respectively, that are specified by a defectivepixel location. When the match unit 240 determines that a match hasoccurred, the match unit 240 asserts a match signal.

When the asserted match signal is provided to the replacement unit 250,the replacement unit 250 provides the output of the consistentreplacement choice facility 254 as the output pixel value. In otherwords, the replacement unit 250 replaces the defective pixel value witha consistent replacement choice (e.g., a previous pixel value), which isdescribed in greater detail hereinafter. The asserted match signal isalso provided to the index manager 238 to update (e.g., to increment byone) the index 239 so that the index 239 points to the next defectivepixel location in the table 230.

It is noted that the match unit 240 is provided with an enable input forreceiving an enable signal that can be used by a designer to selectivelydisable the match unit 240 of the DPDCM 110 of the present invention.When the match unit 240 is disabled, the replacement unit 250 onlyprovides the ADC output as the output pixel value (i.e., the output ofthe consistent replacement choice facility 254 is never provided as anoutput pixel value), thereby effectively disabling the DPDCM 110 of thepresent invention.

Defective Pixel Correction Mechanism 220

In one embodiment, the replacement unit 250 is implemented with amultiplexer 250 that has a first input coupled to the ADC 170 forreceiving the output of the ADC 170 and a second input coupled to aconsistent replacement choice facility 254, and a third input coupled tothe match unit 240. Based on these inputs, the multiplexer 250selectively outputs either the value provided by the ADC 170 or aprevious pixel value provided by the consistent replacement choicefacility 254. The replacement value can be, for example, a previouspixel that is in the same frame, in the same row, and that is apredetermined number of pixels from the current pixel (e.g., two pixelsto the left of the current pixel location).

The consistent replacement choice facility 254 can be implemented with adelay line having a one-back circuit 260 coupled to a two-back circuit264. Upon receipt of a start row signal, the one-back circuit 260 andthe two-back circuit 264 are cleared. Thereafter, the current (N) outputpixel value is provided to the one-back circuit 260 when the N+1 (next)pixel is being processed by the DPDCM 110 and then moved to the two-backcircuit 264 when the N+2 pixel is processed by the DPDCM 110. The valuein the two-back circuit 264 is then provided as one of the inputs to themultiplixer 250. When the match signal is asserted, the multiplexeroutputs the replacement value (i.e., the output of the two-back circuit264) instead of the output of the ADC 170. When the match signal isde-asserted (i.e., the current pixel is not a defective pixel location),the digital pixel value of the current pixel is provided as the outputof the multiplexer 250. When a color filter with Bayer pattern isemployed, the two step delay line provides a previous pixel value havingthe same color as the current pixel that is two pixels to the left ofthe current pixel location.

When either the first pixel location or the second pixel location is anyof the rows is a defective pixel location, the output pixel value isassigned a zero value since two pixels need to be processed for each rowbefore the output pixel value propagates to the output of the two-backcircuit 264.

Defective Pixel Processing

FIG. 4 is a flowchart illustrating the processing steps performed by thedefective pixel detection and correction mechanism (DPDCM) 110 of FIG.2. In step 300, the DPDCM 110 is enabled. For example, an enable signalcan be utilized to selectively enable or disable the defective pixeldetection and correction mechanism 110. In step 304, a plurality ofdefective pixel locations is loaded into the look-up table 230. Forexample, the input/output register 234 can be employed to writedefective pixel locations to the look-up table 230.

The step of loading the defective pixel locations can include the stepof determining the defective pixel locations through a test (e.g., amanufacturing test). When the lookup table 230 is a read-only type ofstorage (e.g., a PROM), then the table is programmed during and/or afterpackage test when the defective pixels are identified.

When the lookup table 230 is a random access type of storage (e.g.,RAM), then the system in which the sensor is embedded identifies thedefective pixels and writes the appropriate values into the RAM duringsystem run-time. Loading the defective pixel locations can be aconfiguration step, an initial run time step, or a continuous process.

In decision block 306, a determination is made whether a new framesignal has been asserted. When a new frame signal has been asserted, thetable index is reset in step 308. Thereafter, processing continues atstep 310. When a new frame signal has not been asserted, processingproceeds to step 310.

In step 310, the current pixel location (e.g., the current row andcurrent column) are received. In step 314, a defective pixel locationpointed to by the table index is received. For example, a row and columncorresponding to a defective pixel location pointed to by the index isaccessed.

In decision block 340, a determination is made whether the current pixellocation matches with the defective pixel location. For example, thisstep can involve 1) comparing the current row with the row of thedefective pixel location (hereinafter referred to also as defectivepixel row); 2) comparing the current column with the row of the columnof the defective pixel location (hereinafter referred to also asdefective pixel column); 3) determining whether there is a match betweenthe current row and the defective pixel row; and 4) determining whetherthere is a match between the current column and the defective pixelcolumn. As described earlier, the defective pixel locations can bestored in the look-up table 230 in a first order (e.g., a sorted order).Each defective pixel location can specify a row and column where adefective pixel may be found.

Step 340 can include the step of asserting a match signal when there isa match and de-asserting the match signal when there is no match. Thematch signal can then be utilized to control the MUX 250 to selectivelyprovide either the output of the ADC 170 or to provide a replacementvalue (e.g., the output of the two-back circuit 264) as the output pixelvalue.

When there is no match, processing continues at step 330, where theoutput of the ADC 170 is provided as the output pixel value. In thiscase, a current pixel location is not a defective pixel location. It isnoted that the detection of defective pixels is stable and consistentfrom frame to frame (i.e., the defective pixel locations arepredetermined and do not vary from frame to frame). Consequently, theconsistent defective pixel detection mechanism of the present inventionreduces or eliminates artifacts that stem from an inconsistent defectivepixel detection scheme. Processing then continues at decision block 306.

When there is a match, in step 344 a previous pixel value is provided asthe output pixel value. Preferably, the previous pixel value is in thesame frame, in the same row, and two pixels to the left from the currentpixel location. In this case, a current pixel location is a defectivepixel location. It is noted that the correction of defective pixels isstable and consistent from frame to frame (i.e., a previous pixel valueis chosen that is a predetermined or a fixed number of pixels from thecurrent pixel location to replace the defective pixel). Consequently,the consistent defective pixel correction mechanism of the presentinvention reduces or eliminates the artifacts that stem from aninconsistent defective pixel correction scheme.

In step 350, an index into the table of defective pixel locations isincremented so that the index points to the next defective pixellocation. Processing then continues at decision block 306.

The defective pixel detection and correction technique of the presentinvention also effectively handles the case of multiple adjacentdefective pixels. The de-mosaicing process tends to smooth out theeffects of adjacent pixels being set to previous pixels (e.g., twopixels to the left of the current pixel location). The de-mosaicingprocess examines surrounding pixels to estimate the color values of eachgiven pixel. For example, when a defective red pixel is set to a valueof a previous red pixel two places to the left of the current pixel, theblue and green values for the current pixel location are interpolatedwith neighbors of the current pixel location and not the neighbors ofthe previous pixel, thereby tending to smooth out the effects of thepixel correction. Consequently, the defective pixel detection andcorrection technique of the present invention allows sensors withclusters of adjacent defective pixels to be hidden from the system.

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. It will, however, be evidentthat various modifications and changes may be made thereto withoutdeparting from the broader scope of the invention. The specification anddrawings are, accordingly, to be regarded in an illustrative rather thana restrictive sense.

1. A method correcting at least one defective pixel of an array ofpixels, comprising the steps of: storing defective pixel locations ofthe pixel array in a table in a pre-arranged order; receiving a currentpixel location from the pixel array; matching the current pixel locationwith a respective stored defective pixel location; and selectivelyreplacing a current pixel value associated with the current pixellocation responsive to the current pixel location matching therespective, stored defective pixel location and a mode signal thatenables replacement of defective pixel values.
 2. The method accordingto claim 1, wherein the step of selectively replacing the current pixelvalue includes substituting the current pixel value with a replacementvalue, the replacement value being based on (1) a pixel value associatedwith a previously received pixel location; or (2) a predetermined value.3. The method according to claim 2, wherein the step of selectivelyreplacing the current pixel value includes: setting a first mode or asecond mode via the mode signal; when the current pixel location matchesthe respective, stored pixel location and the first mode is set,replacing the current pixel value with the replacement value andoutputting the replacement value; and when the current pixel locationdoes not match any stored pixel location or the second mode is set,outputting the current pixel value.
 4. The method of claim 2, furthercomprising the steps of: asserting, via a programmable interface, anenable signal to output the replacement value, as the current pixelvalue when the current pixel location is determined to match therespective, stored defective pixel location; and de-asserting, via theprogrammable interface, the enable signal to output the current pixelvalue when the current pixel location is determined to match therespective, stored defective pixel location.
 5. The method according toclaim 1, wherein the steps of: matching the current pixel location withthe respective, stored defective pixel location includes the steps of:receiving current row and column locations corresponding to the currentpixel locations, and determining whether the current row and columnlocations match pairs of row and column locations for predetermineddefective pixels of the pixel array that are stored in the table; andselectively replacing the current pixel value includes the step of: ifthe current row and column locations match a respective pair of row andcolumn locations stored in the table, replacing the current pixel valueassociated with the current pixel location with the replacement value,the replacement value being one of: (1) a predetermined value; or (2) avalue determined from at least one pixel in a common row with thecurrent row location.
 6. The method of claim 5, wherein the step ofselectively replacing the current pixel value further includes the stepof: receiving, from a timing controller, one or more timing signalsindicating at least a start of a frame, a current row, and a currentcolumn; incrementing, by an index manager, an index position of thetable based on the current row and current column indicated by the oneor more timing signals received from the timing controller; andresetting, by the index manager, the index position of the table to astarting position responsive to the one or more timing signalsindicating the start of the frame.
 7. The method according to claim 5,wherein: when the current pixel location is defective and is located atone of a first column location or a second column location of thecurrent row, the current pixel value is replaced with the predeterminedvalue; and when the current pixel location is defective and is notlocated at one of the first column location or the second columnlocation of the current row, the current pixel value is replaced with apreviously received pixel value.
 8. The method of claim 1, wherein thestep of storing the defective pixel locations of the pixel array in thetable includes the step of: loading into the table, via a programmableinterface, the defective pixel locations of the pixel array one of: (1)at a predetermined time prior to receiving the current pixel location or(2) as a continuous process.
 9. The method of claim 8, wherein thedefective pixel locations of the pixel array loaded into the table arestored and used to correct defective pixels for a plurality of framessuch that the current pixel value in different frames is consistentlyreplaced with the replacement value associated with the current pixelfor each respective frame.
 10. A circuit to correct defective pixels inan array having a plurality of pixels comprising: a defective pixeldetector including a defective pixel table storing predetermineddefective pixel locations, the defective pixel detector sequentiallyreceiving a series of pixel locations from the array; a matching unitmatching respective ones of the sequentially received pixel locationswith respective, stored defective pixel locations; a defective pixelcorrector configured to replace selected ones of the pixel valuesassociated with the matched defective pixel locations with replacementvalues; a mode setting unit to set a first mode or a second mode;wherein: (i) in the first mode, the defective pixel corrector replacesthe pixel values corresponding to the matched defective pixel locationswith replacement values and outputs the replacement values, as outputvalues; and (ii) in the second mode, the defective pixel correctoroutputs the pixel values corresponding to the sequentially receivedpixel locations, as the output values.
 11. The circuit according toclaim 10, wherein each replacement value is: (1) a predetermined value;or (2) a pixel value from a previously received pixel location.
 12. Thecircuit according to claim 10, further comprising a programmableinterface configured to receive a mode signal to set one of the firstmode or the second mode.
 13. The circuit according to claim 12, whereinthe programmable interface is further configured to load predetermineddefective pixel locations into the defective pixel table.
 14. Thecircuit according to claim 10, wherein the defective pixel correctorincludes: a memory circuit buffering a pixel value of a pixel which isin a predetermined location relative to a selected pixel location; and amultiplexer for receiving a match signal in accordance with the modeset, receiving the buffered pixel value and a pixel value associatedwith the selected pixel location and outputting one of the bufferedpixel value or the selected pixel value, as the output value.
 15. Thecircuit according to claim 14, wherein the memory circuit includes aplurality of buffering elements, formed as a delay line, the bufferedpixel value is a pixel value associated with another selected pixellocation received by the multiplexer prior to the selected pixel valueand is input to the memory circuit from the output of the multiplexersuch that each respective buffered pixel value is input to themultiplexer, as one of: (1) a previously received selected pixel valueor (2) a previously input buffered pixel value.
 16. The circuitaccording to claim 10, wherein the multiplexer outputs: the selectedpixel value when (1) the second mode is set or (2) the selected pixellocation does not match any stored defective pixel locations; and thebuffed pixel value when the first mode is set and the selected pixellocation matches a respective, stored defective pixel location.
 17. Thecircuit according to claim 14, further comprising: an index managercoupled to the defective pixel table and the matching unit, the indexmanager receiving the match signal and responsive to the match signalmanages a table index that points to a respective, defective pixellocation in the defective pixel table.
 18. The circuit of claim 17,further comprising: a timing controller, generating at least one timingsignal indicating a start of a frame, wherein the index manager isfurther coupled to the timing controller such that the indexed managerresponsive to the match unit indicating a match, increments the tableindex so that the table index points to a next defective pixel locationin the table and responsive to the start of the frame, resets the tableindex to point to a starting position in the index table.
 19. A methodcorrecting at least one defective pixel of an array of pixels,comprising the steps of: storing defective pixel locations of the pixelarray in a table; receiving a current pixel location from a timinggenerator; determining whether the current pixel location is defectivebased on the defective pixel locations stored in the table; andoutputting, responsive to user selection, one of: (1) a replacementvalue for a current pixel value associated with the current pixellocation, or (2) the current pixel value when the current pixel value isdefective.
 20. Apparatus to correct at least one defective pixel of anarray of pixels, comprising: a defective pixel detector including adefective pixel table storing predetermined defective pixel locations,the defective pixel detector receiving a current pixel location from thearray; a matching unit determining whether the current pixel location isdefective based on the defective pixel locations stored in the defectivepixel table; and an outputting unit outputting, responsive to userselection, one of: (1) a replacement value for the current pixel valueassociated with the current pixel location, or (2) the current pixelvalue when the current pixel value is defective.
 21. A method correctingat least one defective pixel of an array of pixels, comprising the stepsof: storing defective pixel locations of the pixel array in a table in aprearranged order; receiving a current pixel location from the pixelarray; determining whether the current pixel location is a defectivepixel location; responsive to the current pixel location being adefective pixel location, outputting a previous pixel value, as anoutput pixel value; and incrementing, by an index manager, an index ofthe table to point to a next defective pixel location in the tableresponsive to the current pixel location being the defective pixellocation; receiving, by the index manager, a frame starting signal; andresetting, by the index manager, the index of the table to point to astarting position based on the received frame start signal, wherein thelast entry in the table is coded as a location which does not exist inthe array of pixels such that the index is not incremented past the lastentry in the table.
 22. Apparatus to correct at least one defectivepixel of an array of pixels, comprising: a defective pixel detectorincluding a defective pixel table storing defective pixel locations; amatching unit matching received pixel locations from the array withrespective, stored defective pixel locations; a defective pixelcorrector configured to replace a pixel value associated with arespective, matched defective pixel location with a replacement value; atable having an index; and an index manager incrementing the index ofthe table to point to a next defective pixel location in the tableresponsive to the received pixel location being matched to therespective, matched defective pixel location, the index managerreceiving a frame starting signal and resetting the index of the tableto point to a starting position of the table based on the received framestart signal, wherein the last entry in the table is coded as a locationwhich does not exist in the array of pixels such that the index is notincremented past the last entry in the table.